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都知道油船现在都要求双壳，似乎道理很明显，双壳的撞坏了外壳也不会漏油，可一些专家们可不这么认为，大家可曾想过单壳的优点呢？
推荐感兴趣的看看下面这篇文章，看看专家们怎么说，也许与你想的不一样
Single v Double Hull Controversy
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In an attempt to reduce the frequency of oil spills from ocean-going oil tankers, single hulled, ocean-going oil tankers are now being phased out in favour of ocean going double hulled oil tankers. Older tankers are "single-hulled" i.e. they have only one hull. Newer tankers are "double-hulled", with a space between an outer hull and an inner hull to the risk of a spill if the outer hull is breached. This space is used to carry water ballast when the ship is not carrying an oil cargo. In theory the addition of an extra hull should prevent such a ship from suffering a catastrophic breach of the hull. A double-hull tanker is generally safer than a single-hull in a grounding incident, especially when the shore is not very rocky.
（先说普遍的看法是，双壳比单壳安全，尤其是在礁石很多容易触礁的情况下）
But some commentators have questioned whether double hulls are actually any safer than single hulls and put the proposition that double hulls could be more dangerous. Collisions at a low speed won't necessarily damage a vessel. Collisions at a greater force would still have to rupture the internal oil tanks and cause the oil to spill. There is a physical force called 'hydrostatic balance' which basically refers to the (strong) tendency of oil and water to repel each other. Expert opinion (see The Tankship Tromedy by Jack Devanny, ISBN: 0-9776479-0-0, http://www.bookmasters.com/marktplc/01558.htm) points out that hydrostatic pressure within tankers is more than adequate to contain an oil spill in the event of a low impact collision, especially if the internal tanks are set in an elevated position.
（反驳第一段里的说法；低速的碰撞不会破坏船舶，高速碰撞时仍然会使双壳的内部油舱破裂，引起漏油，具体根据是'hydrostatic balance' 原理，详细见Jack Devanny发表的文章，在http://www.bookmasters.com/marktplc/01558.htm）
The case against double hulls can be found, for instance, in the article "Double, double toil and trouble" in Fairplay International Shipping Weekly, 23 Jun 2005. The essence of the case against double hulls is as follows. A single hull is more easily inspected and maintained (remembering also that oil is not carried within big void spaces within a tanker, it is carried within big tanks within the tanker) then are double hulls. Plus the struts between the skins of a double hull are subject to hogging and sagging forces (the tendency to make metal bend down at the ends and up in the middle (hogging) and down in the middle and up at the ends (sagging)), racking and twisting, whereas these forces are non-existent in the case of a single hull tanker. Double hulls also carry a greater risk of explosion than a single hull. Gas from crude oil is flammable and double hulls have void spaces between their skins, whereas single hulls do not (because they don't have two skins). Gas collects within the void spaces and so must be pumped full of inert gas to prevent explosion. None of this applies to single hulls ships.
（继续反驳；有文章指明“Double, double toil and trouble”，单壳检查和维修方便。双壳在单壳和双壳之间有girder等支撑，他们同时也承受着中垂忠拱扭曲作用，而这对于单壳来说，这些作用在支撑上的力都不存在。另外，双壳之间有空间，也就是现在所说的压载舱，油气如果漏到压载舱里，会可能有爆炸危险，而作为单壳来说，则没有这个危险。）
Perhaps the most worrying aspect of double hulls is that they do not offer any protection in the event of a high energy collision or groundings - i.e. in the event of a big crash or grounding oil will spill despite there being a double hull. The great majority of oil spills come from high energy collisions (http://www.earthtoys.com/emagazine.php?issue_number=07.02.01&article=green_ships). A very significant danger posed by double hulls is the free surface water effect. "A double-hulled tanker doesn't need longitudinal bulkheads for longitudinal strength, as the inner hull already provides this. This results in much wider tanks, significantly increasing the free surface effect," writes Earthtoys Emagazine. Free surface water is a very dangerous phenomenon that occurs when water enters into a vessel and is able to flow freely from side to side, or from fore to aft, along with the pitch and heave motion of the sea. When a vessel tilts, the free water rushes from one side of the ship to the other. The sudden rush of water to one side can cause the ship to suddenly list dangerously, even causing it to tip and sink. The free surface water effect, caused by the crew trying to put out a fire, was a significant factor in the sinking of the roll-on, roll-off Red Sea Ferry, the Al-Salam Boccachio '98, which caused the deaths of over 1,000 people.
（接着反驳；对于双壳最大的担心是，双壳在高能量的碰撞下不会提供任何保护，注意，绝大部分的漏油事故都是高能量碰撞造成的，具体根据见http://www.earthtoys.com/emagazine.php?issue_number=07.02.01&article=green_ships。另外一点，就是双壳很典型的一点就是自由液面问题，双壳油船不需要为了总纵强度再设纵向舱壁，因为双壳已经可以保证好了总纵强度，但是这样，舱就太大，非常容易受自由液面影响。而单壳不一样，因为单壳纵向舱壁相对多，舱相对窄，相对小，从而受自由液面影响小。（但事实上这点已经不是问题了，因为现在大油船都不会只弄一个从左到右大舱，一般都分左中右或左右舱，并且舱壁现在都有制荡舱壁anti-sloshing，所以这一点已经大大改进了。））
Owing to the greater use of materials involved, greater hogging and sagging forces, greater likelihood of explosive gas/air mixture building and greater difficulty of inspecting and maintaining double hulls when compared to single hulls, some commentators believe that double hulls are more dangerous than single hulls. Further criticisms of double hulls can be found in "Double Hull Tankers: High Level Panel of Experts Report" (2005) at http://www.emsa.eu.int.
（结论，一些专家仍然相信双壳比单壳危险，更多关于双壳的批评可以看http://www.emsa.eu.int网站上"Double Hull Tankers: High Level Panel of Experts Report" ）
A full investigation of the pros and cons of single v double hulls can be found in an article on green shipping by C. G. (Chuck) Steiner President and CEO WaterSmart Environmental, Inc. The article can be accessed at http://www.earthtoys.com/emagazine.php?issue_number=07.02.01&article=green_ships.
（一个关于single和double hulls正面和反面的文章已经由WaterSmart Environmental公司的主席和首席执行官C. G. (Chuck) Steiner发表，请见http://www.earthtoys.com/emagazine.php?issue_number=07.02.01&article=green_ships.） |
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发表于 2007-8-25 00:00
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